1. Field of the Invention
The present invention relates to a braille printing apparatus, and more particularly to an apparatus that prints not only embossing braille characters but also an embossing figure.
2. Discussion of the Background
Braille is printed as a series of raised dots on a medium such as paper in which each character is represented as a dot pattern, forming the basic braille written units that are read by touch. Special braille writers, braille typewriters and the like are used to write braille. Braille may be printed using a zinc printing plate in which character dot impressions are produced. A typesetting machine is then used to produce a printing plate from the zinc printing plate. The printing plate is then pressed onto the surface of the recording medium, e.g., paper, to produce the printed braille material.
In braille typewriters, braille is printed on a recording medium, such as paper, using a hard braille plate employed as an embossing die and a printing rod having a pin-shaped projection employed as a debossing die.
FIGS. 1(a)-1(c) show a way to print braille in a background braille typewriter. A braille plate 200 has many recesses 200a forming a two dimensional matrix of recesses 200a on the surface of the braille plate 200. A recording medium P, such as paper, is placed on the surface of the braille plate 200, and is pressed by a projection 201 of a printing rod that fits required recesses 200a of the braille plate 200, see FIG. 1(a) and FIG. 1(b), and this results in making an embossing braille P1, see FIG. 1(c).
This type of braille typewriter that makes an embossing at a uniform position fixed by the recesses 200a of the braille plate 200 is used for only embossing braille characters, and cannot be used for embossing a figure. Accordingly, another type of braille typewriter is contemplated that has a braille plate made of soft synthetic rubber so that it can be used for embossing a figure.
FIGS. 2(a)-2(c) show a way to print braille with another type of background braille typewriter. A braille underlay 100 employed in a manner similar to the braille plate 200 of FIG. 1 is made of soft synthetic rubber. A recorded medium P, such as paper, placed on the surface of the braille underlay 100 is pressed by the projection 101a of the printing rod at any required position at will, see FIG. 2(a) and FIG. 2(b), and the result is that an embossing braille P1 is formed, see FIG. 2(c).
FIG. 3 shows a type of background braille typewriter using the soft printing underlay 100 such as is shown in FIG. 2 as disclosed in Japanese Laid-Open Utility Model Application (KOKAI-JITSUYO) 56-24244. In this device the recording medium P is held by a spring 108 on a platen 100 and is pressed by the projection 101a of a printing rod 101 having a pin-shaped projection 101a employed as a debossing die, to make embossing points on the recording medium P. A first pulse motor 102 at one end of spindle 12 of the platen 100 drives the platen 100 in forward and reverse rotations. The rod 101 may be moved by a second pulse motor 107, rod 101 being slidably supported by shaft 104, and rod 101 is connected with wire 106 formed over rollers 105 and 103.
In this type of braille typewriter, the underlay 100 has enough thickness to stop a depth of the embossing and absorb the shock of the pressure of the projection 101a. However, by virtue of the elasticity of the underlay 100, particularly the loss of elasticity of underlay 100 over time, and particularly at areas of heavy use, the depressible depth of the underlay 100 does not become uniform in proportion to a dispersion of hardness of the surface of the underlay 100. In some cases, the projection 101a of the printing rod 101 may tear and break the recording medium P by pressing it too deep.